1. Field of the Invention
The present invention relates to a focus control device for recording or playback of data from a recording medium such as a magneto-optic disk, an optical disk or the like, and, more particularly, the present invention relates to a focus control device to perform focus control with respect to a multi-layer recording medium having a plurality of recording layers.
2. Description of the Related Art
Devices are known for recording data on or playing back data recorded on a conventional type of magneto-optic disk, or the like data recording medium, using a condensed light beam to illuminate a recording surface of the recording medium. During recording or playback of data, focus control is performed such that the condensed light beam has a focus position on the recording surface of the medium.
Various attempts have been made to increase the data capacity of the magneto-optic data recording medium and the like data recording media. For example, one technique considered for attaining a higher data density on a data recording medium is to use multiple data recording layers. However, the focus control with the conventional data recording and playback device cannot be performed to correspond to each recording layer of a multi-layer recording medium because the prior art data recording and playback device has as its object of control a recording medium having a single recording layer.
Therefore, what is needed is a data recording and playback device to control focusing on each recording layer of a multi-layer recording medium.